Method of operating gas discharge panel

ABSTRACT

There is disclosed a method of supplying operating potentials to a gas discharge panel which comprises isolating the signal sources from any direct electrical connection with the gas discharge panel.

White States atet n 1 Schmersal METHOD OF OPERATING GAS DISCHARGE PANEL[75 Inventor: Larry J. schmergai,raieaajoma" [73] Assignee:Owens-Illinois Inc., Toledo, Ohio [22] Filed: Oct. 8, 1971 [21] Appl.No.: 187,863

[52] US. Cl 315/169, 315/153, 315/156 [51] Int. Cl. 1103f 3/68 [58]Field of Search 315/169, 153, 156

[56] References Cited UNITED STATES PATENTS 8/1970 Tarbox et al. 315/153X 3,524,986 8/1939 Hamden, Jr. 250/211 Primary Examiner-Nathan KaufmanAttorney-Donald Keith Wedding et al.

57 ABSTRACT There is disclosed a method of supplying operatingpotentials to a gas discharge panel which comprises isolating the signalsources from any direct electrical connection with the gas dischargepanel.

1 Claim, 1 Drawing Figure PAIENIED JUL 31 I915 METHOD OF OPERATING GASDISCHARGE PANEL RELATED APPLICATION This is an application filed under35 U.S.C. 120 and relates to copending U.S. Pat. application Ser. No.851,131, filed July 18, 1969 now US. Pat. No. 3,628,088.

BACKGROUND OF THE INVENTION Gas discharge panels and devices of thepulsing discharge type (e.g., discharges terminated by stored charges)require relatively high operating voltages, the magnitude of whichdepends upon, among other things, the discharge gap, gas mixture andpressure, thickness of the dielectric. For example, the gas dischargepanel disclosed in the above-referenced Nolan application requiressustaining voltages between about 300-400 volts supplied to conductormatrices defining discharge sites. High voltage pulses are added to suchsustaining voltages at selected times to manipulate discharges atselected discharge sites. Command or information signals from a computeror other source of information to be displayed and/or stored arenormally at a 4 volt level and such low voltages are of insufficientmagnitude to manipulate the discharge condition of selected dischargesites. In the past, low voltage command or address voltages fromaddressing logic circuits have been translated to voltage levelsufficient to manipulate discharges and selected discharge sites bytransformers driven by two transistors. Also, high voltage transistorswitches actuated by the low voltage command voltages are used toconnect a high voltage direct current supply to conductors in thedischarge site selection matrix. In such cases, the low voltagecircuitry may require additional components to assure isolation of thehigh voltage supply from the low level logic circuits.

SUMMARY OF THE INVENTION In accordance with the present invention,isolation of the low level command voltage source is achieved by a useof an optical couple. The low level command signal (4 volts) isconverted to a pulse of radiant energy such as light, which may bedirectly coupled, or, preferably, transmitted by a fiber optic element,to a light sensitive transistor amplifier so that the low level commandsignal source is electrically isolated from the high level operatingvoltage, permitting different referenced grounds. Thus, the low voltagesystem can be earth ground referenced whereas the light sensitivetransistor amplifier can be referenced to the high level periodicvoltage necessary to sustain discharge within the discharge device at aselected site, once initiated.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features, aspectsand details of the invention will become more apparent from thefollowing specification when considered with the accompanying drawingillustrating a preferred embodiment of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT With reference to the drawing, agas discharge panel of the type disclosed in Nolan application Ser. No.764,577 is constituted by a pair of relatively rigid support or platemembers 1 l and 12, respectively, each of which has on opposing surfacesthereof conductor arrays 13 and 14, respectively, cooperatively definingdischarge site locations and a pair of thin dielectric members 15 and16, respectively, plate member 11 and 12 being joined together andsealed by spacer sealant member 17. The opposing surfaces of thindielectric members 15 and 16 constitute at least in part a portion ofstorage member forming walls of a thin gas chamber under about 10 milsthick, and preferably the gas chamber is about 4 to 6 mils thick.Transversely oriented conductor arrays 13 and 14 are supplied withoperating potentials for selectively effecting discharges within thethin gas chamber between selected cross points or matrix points of apair of the conductors of each array and sustaining and terminatingdischarges once initiated. The gas is one which is under a relativelyhigh gas pressure so as to localize the discharges within the chamberand to confine charges produced on discharge to within the volume of gasin which they are created As set forth in the aforementioned Nolanapplication, the gas in the thin gas chamber has a breakdown voltageverses pressure-time-discharge gap distance which is relativelyhorizontal over a selected broad range of gas pressure and, preferablyis a mixture of neon and argon gases wherein the neon constitutes about99.9 percent atoms of the gas mixture and the argon constitutes about0.1 percent atoms of the gas mixture. The gas is under pressure of about0.2 atmosphere to about 5 atmosphere and preferably from about 0.2atmosphere to about 1 atmosphere.

As further disclosed in the aforementioned Baker et al. and Nolanapplications, charges produced on discharge of the gas are collectedupon the discrete surface areas of dielectric members 15 and 16 and ineffect constitute electric potentials opposing the potentials whichcreated them and hence terminate the discharge. However, on a succeedinghalf cycle of applied potential, potential of the stored charges, beingin the same direction, aid in initiating the next discharge andconstitute an electrical memory. Because of the gas being at arelatively high pressure and separated from the operating conductors bydielectric material, relatively high periodic alternating potentials arerequired in order to sustain discharges once initiated. At the presenttime, typical sustaining voltage for a neonargon panel lies within therange of 335 to 350 volts peak to peak at a frequency or rate of fromabout 30 to 50 kI-I with 2 microsecond high voltage pulses superimposedor added to the sustaining voltage to manipulate the discharge conditionof selected discharge sites. The normal magnitude of pulse potentialrequired to initiate a discharge (assuming, of course, that the gas hasbeen conditioned by ultra-violet or by other means as disclosed in theaforementioned patent application) is about the same as the sustainingpotential.

Normally voltages from a computer or standard commercially availablelogic circuitry is in a neightborhood of 4 volts. In order to interfacesuch low level signals with panels requiring voltages around timeslarger is the problem with which the present invention deals.

As shown in the drawing, each conductor 14-1, 14-2, 14-3 M-n ofconductor array 14 and each conductor 13-1, 13-2, 13-3, and 13-n ofconductor array 13 is provided with its own drive circuit.

Each row conductor in conductor array 14 and each column conductor inconductor array 13 is provided,

with its own driving or interface circuit, which in the drawing aredesignated as 20-1, 20-2, 20-3 and 20-n for row conductors 14-1, 14-2,14-3, 14-n, respectively, and 2l-1, 21-2, 21-3 and 2l-n for columnconductors 13. It will be appreciated that panel will usually have manymore conductors and conductor arrays 13 and 14, presently availablepanels having the conductors on 30 mil centers so that in a 4 inchdisplay area in a panel there may be about 132 row conductors and 132column conductors.

Interface circuits include a switching transistor of the NPN type havingits collector C connected through resistor 31 to the positive terminalof a high voltage direct current source 32 (E and its emitter Econnected to the negative terminal of high voltage direct current source32. In addition, a periodic voltage, as for example, a sinusoidalvoltage (Vs/2) from a sustaining voltage generator 33-A is applied tothe common terminal 35 or connection between the negative terminal ofbattery 32 and the emitter electrode of transistor 30. As will bedescribed later herein, the sustaining voltage from sustaining voltagegenerator 33-A constitutes 'z the sustaining potential necessary to beapplied across the gas in the-discharge gap in the panel to sustaindischarges once initiated. Oppositely phased sustaining voltage (Vs/2)from sustaining generator 33-B is applied to column conductors 13through addressing pulse circuits 21.

Connected in parallel with the high voltage direct current source 32 isa series circuit constituted by resistor 34 and photosensitive diode 36,the anode of diode 36 being connected to the common circuit point 35 foremitter electrode of transistor 30, the negative terminal of high directcurrent source 32 and the connection from sustaining generator 33-A. Thecommon point 37 between resistor 34 and photosensitive diodes 36 isconnected by a lead 38 to the base of transistor 30.

When photosensitive diode 36 is not illuminated, the resistance thereofis in the megaohm range and all of the current lb enters the base b oftransistor 30 turning this transistor on. Thus, the output voltageappearing at the collector of transistor 30 is essentially thesustaining voltage (Vs/2) from the sustaining generator 33a, passed bytransistor 30.

Photosensitive diode 36 receives signal inputs in the form of burst ofradiant energy, such as light, from a light bearing fiber optic element40, photosensitive diode 36 being in close optically coupled relation tothe output end -0 of fiber optic element 40. The input end 40-I of lightbearing fiber element 40 is in close optically coupled relation withrespect to light emitting diode 41, therebeing a light emitting diode 41and fiber optic element 40 corresponding to each circuit 20 with thecathodes thereof commonly connected together and to the common systemground. Any 4 volt pulse as for example, a 4 volt logic pulse fromlogic-addressing circuit causes the light emitting diode to which it isapplied to emit light. Such light is coupled by a fiber' optic element40 to photosensitive diode 36 to cause the resistance thereof to dropfrom in the megaohm range to about 10,000 ohms which then causes thecurrent lb to flow to ground through photosensitive diode 36. As aresult, transistor 30 is turned off and the output voltage rises to thepotential of high voltage direct current source 32 added to thesinusoidal voltage from sustaining voltage generator 33-A. Thus, thisoutput voltage now consists of a sine voltage plus an additive voltage(e.g., Vs/2 B). When the diode 41 is pulsed by 4 volt logic signals,then the output voltage Vs/2 will also have pulses added thereto of amagnitude essentially equal to source 32.

As noted earlier, the sustaining voltage sources 33-A and 33-B produceoppositely phase sustaining voltages so that k the required sustainingvoltage is applied to column conductors 13 and k the required sustainingvoltage is applied to row conductor 14. In order to accommodate thisarrangement, pulsing circuit 21 utilizes PNP transistors 30, andopposite polarity high voltage direct current source 32' as well as anoppositely poled photosensitive diode 36', and except for this reversalof polarity, the operating principles are identical, it being understoodthat logic signal voltages applied to light sensitive diodes 41 areapplied simultaneously to selected pairs of conductors, the crossingpoints of which defines a selected discharge site which it is desired tomanipulate the discharge condition thereof.

It will be appreciated that other than sinusoidal voltages may be usedto supply sustaining potentials. For example, alternating polaritysquare waves may be used in place of a sine wave. It will also beappreciated that signal produced at the base of transistor 30 may beused to switch a current pulse through a transformer primary to inducehigh voltages in the secondary thereof, the secondary being connected inseries with a source of sustaining voltage as shown in application Ser.No. 699,170.

A feature of the circuit is that a 4 volt pulse, referenced to ground,may be used to control a very high voltage (300 volt) pulse that isreferenced to or floats on a sine wave fonn or other periodic wave form.The fiber optic elements effectively isolates the two signals such thata 300 volt signal does not couple back into the 4 volt system. Inaddition, there are fewer components per interface circuit and,obviously, since transistor 30 is conducting when it is not pulsed, theline impedance is reduced thereby reducing cross-talk between matrixconductors. In the circuit disclosed, the high voltage pulsing circuitis isolated from the source of control signals via the optical couplingbut other forms of isolation may be used so as to permit the pulsesignals to be referenced to the sustaining voltage.

I claim:

1. In a method of supplying operating potentials to a gas dischargepanel device of the type in which a thin gas discharge medium underpressure and bounded by dielectric charge storage members has thedischarge condition of selected discharge sites therein manipulated byselectively applied high voltage pulses and pulse discharges maintained,once initiated, by a pair of relatively high, periodic sustainingvoltages from a pair of sources by means of a pair of transverse row andcolumn conductor arrays the cross points of which define the dischargesites and wherein voltages from a relatively low voltage electricalsignal pulse source determine the occurrence of said high voltage pulse,each source of sustaining potential having a pair of output terminalsfrom each source of sustaining potential to each other and a point ofcommon potential so that said relatively high sustaining voltage sourcesbeing connected to conductors of said array respectively such that saidpanel floats with respect to a point of common potential, supply atleast a pair of relatively opposite polarity high voltage pulses from apair of generators to the row and column conductor arrays, and includingcausing the respective ones of said high voltage pulse geneator means tobe responsive to control signal high voltage electric signalconstituting said high voltage pulses having as a reference point theinstantaneous magnitude of said periodic voltage from the one of saidpair of sources, respectively, to thereby electrically isolate said lowvoltage signal sources from any direct electrical connection with saidpanel device.

1. In a method of supplying operating potentials to a gas dischargepanel device of the type in which a thin gas discharge medium underpressure and bounded by dielectric charge storage members has thedischarge condition of selected discharge sites therein manipulated byselectively applied high voltage pulses and pulse discharges maintained,once initiated, by a pair of relatively high, periodic sustainingvoltages from a pair of sources by means of a pair of transverse row andcolumn conductor arrays the cross points of which define the dischargesites and wherein voltages from a relatively low voltage electricalsignal pulse source determine the occurrence of said high voltage pulse,each source of sustaining potential having a pair of output terminalsfrom each source of sustaining potential to each other and a point ofcommon potential so that said relatively high sustaining voltage sourcesbeing connected to conductors of said array respectively such that saidpanel floats with respect to a point of common potential, supply atleast a pair of relatively opposite polarity high voltage pulses from apair of generators to the row and column conductor arrays, and includingcausing the respective ones of said high voltage pulse geneator means tobe responsive to control signal pulses and to generate high voltagepulses having as a reference point the instantaneous magnitude of saidvoltage periodic voltage from the one of said pair of sources it isconnected with in series relation, the improvement comprising the stepof converting each said low voltage electrical signal pulse,respectively, to a nonelectric signal pulse, conveying said non-electricsignal pulse along a fixed path and then converting said non-electricsignal pulse to high voltage electric signal constituting said highvoltage pulses having as a reference point the instantaneous magnitudeof said periodic voltage from the one of said pair of sources,respectively, to thereby electrically isolate said low voltage signalsources from any direct electrical connection with said panel device.